You need to have some items and customers before you can create a sales quotation.

Also use a Chart of Accounts that matches the en_US-new.sql for tables, fields, field types and fields orders apart from missing SysPrefs entries fixed. Checkout the latest Charts from here.

Fresh install of 2.4.3.

When attempting to modify the price list on sales quotation that are already created I have noticed the fields on the header section are greyed out except for the Reference field. 

Thanks
Jack